Power-transmission apparatus



July 27, 1948. HOBBS 2,446,088

POWER THANSMISS ION APPARATUS Original Filed Nov. 3, 1941 4 Sheets-Sheet 1 u 27, 1948- H. F. HOBBS 2,446,088

POWER TRANSMISSION APPARATUS Original Filed Nov. 3, 1941 4 Sheets Sheet 2 d 3i /-L /71 unuuun mm 11 n nn H u u n u u n n m: 1

JMW I A a M y' zms H. F. HQBBS 2,446,088

POWER TRANSMISSION APPARATUS 4 Sheets-Sheet 3 Original Filed Nov. 3, 1941 1 Jul 27,1948. H. F. HOBBS 2,446,088

rbwian TRANSMISSION APPARATUS I I Original Filed Nov. 3, 1941 4 Sheets-Sheet 4 71366 6&2 6

Patented July 27, 1948 rowaa-rms mssron APPARATUS Howard Frederick Hobbs, Leamington Spa, England, assignor, by

direct and mesne assimments, to Hobbs Transmission Limited, Leamington Spa, England, a British company Original application November 3, 1941, Serial No. 417,739. Divided and this application April 28, 1944, Serial No. 533,

March 24, 1941 The invention relates to power transmission apparatus such as clutches, variable speed gears, and variable torque/speed gears and its main Claims. (01. 14-359) object is to enable a clutching action (e. g. for

effecting gear changes) to be effected in a small space and without manual effort. It is usually particularlydifficult to have the necessary mechanism in a small space when more than four forward speeds are provided in a gearbox and the present invention enables this to be more easily accomplished with saving of space, weight of metal, and length of shafts.

According to the present invention I provide an apparatus having an input shaft, a layshaft, an output shaft, gear wheels mounted on all said shafts and some at least of which are free on the respective shafts and at least two said gear wheels being permanently in gear with other of two said gear wheels, a pair of sets of clutch teeth mounted on the layshaft adapted to be clutched together by sliding axially into engagement, a pair of sets of clutch teeth mounted on one of the other shafts adapted to be clutched together by sliding axially into engagement, at least one further pair of sets of clutch teeth mounted on at least one of said shafts adapted to be clutched together by sliding 189. In Great Britain engaged by the action of the springs alone and/or to prevent the teeth from engaging on application of fluid pressure.

In order that the invention may be clearly understood and readily carried into effect, I will describe constructional form thereof with reference to theaccompanying diagrammatic drawings wherein Figure- 1 is a vertical longitudinal sectional view of the front part of a gear made in accordance with the invention:

Figure 2 is a similar view of the rear part of the gear;

Figure 3 is a view of a detail to be described.

Figure 4 is a view of a modified form of the front part of the gear:

Figure 5 15a view of a modified form of the rear part of the gear; a

Figure 6 is a vertical section view of a control mechanism for us with a clutch type distributor;

Figure 7 is a section on line 1-1 on Figure 6;

Figure 8 is a. section on line 8-8 on Figure 6.

The input shaft A drives the distributor shown in Figure 1 which can distribute the power accordaxially into engagement, operative connections from said sets of clutch teeth to the respective free gear wheels and their respective shafts whereby said free gear wheels can be operatively fixed to their respective shafts through said teeth whereby at least three different gear ratios are ing cylinder at least one of which is movable by fluid pressure to bring the sets of clutch teeth into engagement with each other, at least three spring means associated one with each movable member and adapted to effect disengagement of the clutch teeth, and means for applying fluid pressure to each said pair of members for effectteeth to be forced out of engagement on removal of fluid pressure should they fail to become dising to five different ratios to the two output shafts C, D (C being a sleeve surrounding D but the distributor can be reversed so that. the shaft A is used as the output shaft. l

The shaft A drives the distributor casing, l which carries five pairs of friction clutch rings 2, 3; 4, 5; 6,1; 8, 9; and I0, I I. Five corresponding friction plates [2, i3, I4, l5 and it, are disposed one between each pair of clutch rings. The clutch rings 3, 6, 1,9, and II, are carried respectively by pressure rings 20, 2!, 22, 23, and 24, that are carried by the casing i in an axially slidable manner and can be actuated by low pressure of fluid for gripping the clutch plates. For this purpose the five pressure rings are associated with five conduits for fluid and one of these is shown comprising holes 21, 28, 29, 30, in the casing, annular port 3! in a ring 32 which is pressed against the casing by a spring 33, and hole 34. The ring 32 has five annular ports such as 3| and five holes (or sets of holes) such as 34 and the latter communicate with a pump through a con trol'valve not shown in Figure 1. The clutch surfaces can be separated when not in use by springs of which one (36) is shown carried on a bolt 31. The fluid acts between th pressure rings and partition walls 40 carried by thecasing.

The clutch plates 12 and it are fixed respectively' to shafts D and C. Clutch plates i3 and ii are carried respectively by the bevel ,gear wheels 42, 43, of a differential gearing the pinion gaged. All power passes through the shaft C.

2. Clutch I! only is engaged. Transmission occurs through 4!, 45, 44, 48, 49, 50, to drive the shafts C and D diil'erentially with more torque transmitted to C than to D.

3. Clutch ll only is engaged. Transmission occurs through 44, ll, 49, 50 to drive the shafts C and D differentially with half the torque going to each.

4. Clutch l3 only engaged. Transmission occurs through 42, 4!,- I8, 49, 50, with more torque passing to D than C.

5. Clutch i2 only engaged. Transmission all power to shaft D.

These five methods-of distribution are applied between each two adjacent ratios in the gearbox.

One example of a suitable gear-box is shown in Figure 2 in which the shafts C and D are continuations of the shafts C and D in Figure 1.

The shaft or sleeve C carries a gear wheel 60 that gears permanently with a toothed wheel 8i that is carried loosely on a layshaft 84 but can be clutched to the layshaft. The shaft 0 also loosely carries a gear wheel 82 that can be clutched to it and which is permanently in mesh with a toothed wheel 63 fixed to the layshaft 84.

The shaft D carries a fixed gear wheel 68 that can be clutched to the output shaft F and also meshes permanently with a toothed wheel 81 that can'be clutched to the layshaft. A gear wheel 89 is loosely carried by the output shaft and can be clutched'to the output shaft and also meshes with a toothed wheel ll slidably attached to the layshaft. A reversing gear ll, 12 is slidably mounted on a separate shaft and is brought into operation by disengaging Ill from ll and engaging II with II and 12 with III. A

neutral condition is obtained by sliding gear out of mesh with IS.

The clutching of the wheels ll, 62, 68, 61 and 8!, is effected in all cases by generally similar means comprising one element 15 of a dog clutch fixed to the shaft and the corresponding dog clutch element Ii carried by a ring 10 axially slidable in the wheel. These two elements l5, 18 each have an annular set of clutch teeth adapted to engage with each other by the axially slidable movement. The ring ll carries an axially displaceable synchronising ring 80 the two rings being normally held against relative displacement by a springpressed ball II. The ring 18 comprises a piston carrying one set of clutch teeth (18) and working in a cylinder formed by recessing the wheel 82 and leaving a space 11 between the end of the cylinder and the piston. Fluid under low pressure (e. g. 40 lbs. per square inch) is introduced to a space l1 and presses the ring or piston II and ring III on the one hand and the cylinder 0r wheel I! on the other hand in opposite directions against friction rings 83, II, respectively. which tend to synchronise the speed of the wheel with that of parts ll, that are fixed to the shaft. As the pressure increases the ball II is repressed to allow the ring CI to 4 r move so as to bring the set of dog clutch teeth 18 into engagement with theset of teeth 1!. Springs 89,, 90. effect declutching and restore ,the parts to their normal positions when pressure is released. The pressure is distributed from the same valve that distributes fluid to the conduits 34 of the distributor gear.

The clutch engaging loads are wholly selfcontained between parts fixed on the appropriate shafts, e. g., the engaging loads of the clutch I5, 16, is contained between the parts 88, I! that are fixed on'the shaft C. The clutch teeth may have an appreciable angle as shown in Figure 3 for easy engagement and to give slip if overloaded, also to ensure that the clutches will be self-disengaging on release of the end pressure.

The ratios are obtained as follows:

With clutch l8 of the distributor engaged all power is passed through the shaft 0.. With 02 free and BI and 88 clutched a drive to the output shaft ensues through 60, 8|. 84, 10 and-l9. The gears 68, 61 are also clutched to the layshaft but the shaft D runs free in the distributor. The distributor clutch I5 is now engaged and I8 disengaged whereupon some power passes as before to the output shaft through C, 60, GI, 84, I0, 68, and some power passes also through D, 88, ll,

'64, I0 and 69 to the output shaft.

The distributor clutches l4, l3, l2, are engaged successively without altering the gearbox. When I2 is engaged all power passes through D, 66, 61, I0, and 69 leaving the shaft C under no load whereupon gear 62 isclutched to the shaft C and 6| is declutched. The distributor clutches l3, l4,

I5, l6, are then successively engaged whereby full power is again brought onto the shaft C leaving D under no load and at this time 66 on shaft D is clutched to the output shaft, and 61 is released. The distributor clutches are again progressively brought into action until when I2 is again engaged all power passes through D, and direct solid drive ensues. At this time the gears 62, 68, 61, are clutched to their respective shafts and 88 is released and then the distributor system is again used producing an overdrive which is finally at its maximum when I6 is engaged and all power is transmitted through C, 62, 63, 64, 61, and it, Thus there are seventeen different overall ratios.

It should be appreciated that, because of the power passing to the dog clutch to be engaged a e. g. about V4 of the total. The synchronising clutches can in fact conveniently be of such size as almost to carry this portion of the total power, thus permitting only sufilclent slip to enable engagement of the dogs to be made. Thus, for example, large track speed difference in a "tank can be brought about in a comparatively short time. Excessively large power circulation between the tracks can, if desired, cause slip in the dog clutches. f

Figure 4 shows amodified form of distributor in which only three clutches are provided and a single differential. The numerals corresponding to similar parts in Figure 1 except I66 which indicates bob weights which hold the clutch normally out of engagement.

' ly diiierent positions.

shown at 339 and outlets at 384, 385. Relief through ports 386, 381.

The gear-box similarly mayhave any suitable number of gear changes. Figure 5 for example shows a lay-shaft gear-box in which the shafts C,

D, each carry a single gear wheel I52, I53. The output shaft I63 carries the gear IGI' and the layshaft I32 carries gears I63, I64, and I86. The gears I63, I84, mesh with I52, I53, and the gear I36 meshes with the output gear (6|. Gears I33,

l3l have clutches for clutching to the output shaft and I94 has a clutch for clutchingto the layshaft. When combined with the distributor shown in Figure 4, the apparatus gives seven speeds forward and three reverse with only six gear wheels carrying one set'of the clutch teeth integrally whilst the cylinder is formed separatelyor by recesslng the appropriate gear wheel. Engagement of the sets of clutches operatively connects the appropriate gear wheels to their respective shafts and disengagement of the clutches allows the gear wheels to run free. Thus the gear wheels can be permanently in mesh and not disengaged by axial sliding movement and accordingly numerous gear wheels can be accommodated in a small space.

A valve control apparatus for controlling gear changes with a fluid type distributor is shown in Figures 6 to 8. A simple 313 carries the driving gears 31! and 312 of two gear pumps, also spider 314 (one arm only shown) of a centrifugal governor comprising bob-weights 313, disc 315 and ball 319. Piston valve 311 seats on ball 316 and is held in position by spring 318. A rod 383 may be operated by manual control andjthe piston valve held in the open position against the action of the bob-weights. The bob-weights carryprojections 31a which contact with an abutment 31b on the spider 314 when fully outwards and the bob-weights seat on' the spider when fully inwards. They are held inwards at lowspeed by gravity and spring 318. Spider 315 rotates with the bob-weight but is free to adjust its. position on ball 318, should the bob-weights take up slight- Intake to the pumps is valves (not shown) are provided in the outlets. Fluid under pressure is delivered to rotary valves 392, 393, from the pump outlets through drillings to the collector grooves 396, and thence by cutaway such as 399 to the distributor grooves 393. Grooves 39! are exhaust grooves which exhaust The valve 382 directs fluid to a gear-box such as shown in Figure 2 and the valve 383 to a distributor such as shown in Figure 4. The rotary valve 392 cooperates with a casing 350 which has output ports M, N, O, P, Q, which communicate respectively with the five gear-box clutches and will require to be operated in the order MNQ; NQO; QOP; and OPN. The

rotary valve therefore leads pressure to ports M, N, and Q together. The ports N, P, are connected through a ball valve to a common pipe leading to the clutch concerned; the valve prevents connection of one port N to exhaust whilst,

the other is connected to pressure. Movement of, the valve will first open M to exhaust and then 0 to pressure and so on and will thus be required complete range. The valve 333 cooperates with a casing "I having outlet ports R, S, T, leading to the three clutches respectively and required to apply the pressure to the distributor clutches in the order R, S, T, S, R, S, T, S, R. The rotor 393 is drilled from one side to the other so that after one half revolution is made pressure is again fed to the same ports, thus the nine engagements will be made on one revolution of the rotor. The rotor distributor port is arranged to simultaneously shut say port R and open port S, or overlap or lag can be provided according to the width of the distributor port in the rotor. A control lever 333 carries the gear segments engaging pinions 389, 393, which are of suitable size to cause the desired amount of rotation .of each valve. The control member 388 also carries teeth .395 which engage a piston 39l in a cylinder which is connected to the pump delivery by drilling 393 which has a non-return valve 392. A leak 394 is provided in the valve seat. In operation at low engine R. P. M. the valve 311 allows the fluid delivered to the distributor control valve to exhaust through 388, 319 and 381'. The distributor clutch is therefore not engaged although selected by the control until engine R. P. M. are such as to close the valve 311. When this valve is closed pressure is led to the clutch which is engaged. Pressure is also led to the piston 39i so that when the controllever is moved to a position causing a change to be made in the gear-box, a tooth 395prevents the control from rapid movementto a position causing a change of the distributor clutches, as the piston 39I must displace the fluid through the leak 39. Thus, the size of this leak can be arranged to cause suflicient delay to ensure that the new gear train is synchronised and engagement made before power can be applied to it, i. e. transmission must continue through the other engaged train. Such delay will of course be of but a fraction of a second duration. Further smaller teeth may be provided on control 388 or elsewhere on the control parts to position the valve at each torque ratio position.

The ports M, N, O, P, Q, correspond forexample to the clutches for the gear wheels 61, 61, 62, 66, and 69, respectively, in Figure 2, and port R, S, T, correspond respectively to clutches I6,

I4, I! shown in Figure 5.

wheels mounted on all said shafts and some at least of which are free on the respective shafts and at least two said gear wheels on the layshaft being permanently in mesh with gear wheels on one of said other shafts, a pairof sets of clutch teeth mounted on the layshaft adapted to be clutched together by sliding axially into engagement, a pair of sets of clutch teeth mounted on one of the other shafts adapted to be clutched together by sliding axially into engagement, at least one further pair of sets of clutch teeth mounted on at least one of said shafts adapted to be clutched together by sliding axially into engagement, operative connections from said sets of .clutch teeth to the respective free gear wheels and their respective shafts whereby said free gear wheels can be operatively fixed to their respective shafts through said teeth whereby at least three dlflerent gear ratios are obtainable by appropriate disengagement and engagement of the sets ,of clutch teeth. at least three pairs of members associated one pair with each pair of sets of clutch teeth and each pair of members comprising a piston and a cooperating cylinder at least one of which is movable by fluid pressure to bring the sets of clutch teeth into engagement with each other, at least three spring means associated one with each movable member and adapted to effect disengagement or the clutch teeth, and means for applying fluid pressure to each pair of members for effecting engagement of said sets of clutch teeth and adapted to urge the teethinto engagement whilst they are clutched together.

2. A power transmission apparatus comprising a shaft, a clutch member fixed on the shaft and having a set of clutch teeth, a gearwheel loosely mounted on the shaft, a second clutch member housed in the gearwheel and having another set oi clutch teethadapted to engage the first mentioned teeth, means to permit axial-but preventing rotary movement of the second clutch member in relation to the gearwheel, said second clutch member comprising a piston and the gearwheel comprising a cylinder for the piston so that fluid introduced into the cylinder presses the piston to engage the clutch, means for synchronizing the speeds of the two clutch members, means to prevent engagement of the clutch teeth until after operation of the synchronizing means, and a spring for moving the second clutch member in the disengaging direction.

3. A power transmission apparatus comprising a shaft, a clutch member fixed on the shaft and having a set of clutch teeth, a gearwheel loosely mounted on the shaft, a second clutch member housed in the gearwheel and having another set clutch teeth adapted to engage the first mentioned teeth, means to permit axial but preventing rotary movement of the second clutch member in relation to the gearwheel, said second clutch member comprising a piston and the gearwheel comprising a cylinder for the piston so that fluid introduced into the cylinder presses the piston to engage the clutch, means for synchronizing the speeds of the two clutch members. meansior introducing fluid under pressure into the cylinder,

means to prevent engagement of the clutch teeth 4 nizing means to bring about substantial synchronization of the speeds of the said clutch members before said pressure moves said members into en- -l lumber 4. A power transmission apparatus accordin I to claim 2, in which at least a number of the clutch teeth are shaped to enable the teeth to-be forced out of engagement on removal of fluid pressure should they fail to become disengaged by the action of the springs alone and so as to prevent the teeth from engaging on application of the fluid pressure until synchronization is efiected.

5.- A power transmission apparatus comprising a shaft, a clutch member flxed on the shaft and having a set 01' clutch teeth, a gearwheel loosely mounted on the shaft, a second clutch member housed in the gearwheel and having another set of clutch teeth adapted to engage the first mentioned teeth, means to permit axial but preventing rotary movement of the second clutch memher in relation to the gearwheel, said second clutch member comprising a piston and thegearwheel comprising a cylinder for the piston so that fluid introduced into the cylinder presses the piston I to engagethe clutch, means for synchronizing the speeds ot the two clutch members, means to prevent engagement of the clutch teeth until after operation of the synchronizing means, and a spring for moving the second clutch member in the disengaging direction.

HOWARD FREDERICK HOBBS.

REFERENCES CITED The following references are of record in the tile oi this patent:

UNITED STATES PATENTS Name Date 1,894,448 Sitney Oct. 18, 1921 1,449,819 Higinbotham Mar. 27, 1923 1,472,930 Mayer Nov. 6, 1923 1,953,568 Rose Apr. 3, 1934 1,953,628 Padgett Apr. 3, 1934 2,055,970 Fippard Sept. 29, 1936 2,065,224 Hladik Dec. 22, 1936 FOREIGN PATENTS Number Country Date GreatBritaln Jan. 31, 1935 

